The Curious Case Of Steve Rogers
by multi-fandom-crazy-fangirl
Summary: The super soldier serum turns Steve into a part-time vampire (because that's a thing) and Natasha helps him get his sex mojo back. [Vampire/Succubus Steve]
**Well, hello, dear reader.**

 **Whatever made you choose to read this, I don't know. This is weird shit. I apologise beforehand for it. If you manage to read this insanity and leave behind some (hopefully loving) remarks, thank you. If you can't handle this shit, press Alt+F4, and I wouldn't hold it against you.**

 **This is only the first in the super crazy set of alternate universe ideas I have. Hopefully, the others will come around soon too. I use a mix of British and Indian English, and I really don't have it in me to start removing the 'u's from my words. I'm also excessively comma-friendly. Deal with it. Or don't. Your choice.**

 **Well, the story awaits you.**

 **Love, Sakshi.**

 **Summary:** _The super soldier serum turns Steve into a part-time vampire (because that's a thing) and Natasha helps him get his sex mojo back._

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Feeling 'urges' when you're travelling across the country with a dozen scantily-clad showgirls is normal, Steve reasoned. In fact, it was expected. Especially since said scantily-clad showgirls loved to give him a show every now and then since the serum buffed him up.

But when he started feeling newer, different urges in the middle of fulfilling the aforementioned urges... yeah, that was when Steve knew something had gone seriously wrong with Dr. Erskine's serum.

He wasn't naive; he had expected some side-effects of the experiment. The increase in his appetite was expected, given that his metabolism had increased ten-fold. Even the change in his libido didn't really surprise him. No, it was the sudden need to sink his teeth into his partner's neck and taste her as her inner walls clenched around his enhanced girth in sweet release that got him panicking.

In hindsight, he should've known an experimental drug was bound to go wrong on the first try.

So he convinced poor dazed little Greta, the dancer he had unintentionally scarred, literally and metaphorically, that she just brought out his inner animal in bed and it would be their little secret. After he sent the giggling showgirl off with a promise of another animal romp in the sheets, he ran to find Howard Stark because, well...who else could he go to really?

"I'll be damned!" Howard exclaimed, a little too gleeful for Steve's liking. "You're Nosferatu! I helped bloody create Nosferatu!"

But he wasn't, not really. As Steve soon realised, he didn't get these 'urges' all the time. Not when he was eating real, actual human food – food meant to be eaten by humans, not, you know, humans who were food – or when he was around soldiers bleeding half their bodies' worth blood away. In fact, a few days without a recap of the incident had him thinking that maybe, just maybe, it had been a one time thing.

But then Dorothy-the-showgirl-at-the-left-end-of-the-stage is latched onto him and climbing him like a serpent around a tree – Jesus, he needs to stop thinking of his bed partners in such a way – and she's just reached her high and he has to clench his fists and grit his teeth to keep his lips from wrapping around the throbbing pulse point in her long neck and just drawing from her... He doesn't find his own release that night.

After consulting Stark about it – although consulting Howard Stark about anything is just laying his own bed of thorns – he decides to conduct an experiment.

If only America knew that their idol was running around sinking his teeth into unsuspecting women in his free time...

When he woke up in 21st century, he was broken and lost. The psychiatrists that S.H.I.E.L.D. sent his way diagnosed him with PTSD and clinical depression and possibly the worst case of survivor's guilt in history. He lost the drive to do anything but sit alone on his couch and reminisce. Occasionally he went down to the gym in his apartment complex – because those were a thing in this new era – and punched the shit out of a – or ten – punching bags.

But a global catastrophe lurked around the corner, and Captain America was back on track. He was introduced to Agent Phil Coulson – and the concept of a...fanboy? – and Howard's son was flying around in a metal suit and a scientist who apparently dedicated his life to studying Steve's was turning into a giant green rage monster while aliens – aliens! - were turning highly trained S.H.I.E.L.D. operatives into metaphorical flying monkeys...

But he was really thrown in for a loop when he was introduced to a certain red-head on top of an invisible flying submarine.

He hadn't had any urgings since waking up. Steve had believed the problem to have been solved. He'd practically forgotten about it. Till Natasha Romanoff walked up to him – really she was walking up to Coulson but he liked to think she was coming for him – on the deck of the helicarrier and the light breeze brought him a whiff of a subtle scent that was uniquely her and suddenly those urges that had lain dormant inside him had turned into full blown cravings.

It's easy to ignore one's own needs when faced with invading alien armies and a diva of a villain, but afterwards – not so much. Especially not when you're working as closely with the reason behind your raging hard-on – and yes, your bloodlust – almost every day in jobs that only serve to amplify the cravings with every shot of adrenaline in their veins.

What made it worse was that Steve couldn't find sexual gratification anymore. Not with 'professionals' in 'discreet' bars, not with his hand, and it just felt wrong to chase after a woman who was now becoming something of a friend to him. So he tried to move past that and focus on building friendships in a new world. It wasn't like he needed the blood – or the sex for that matter – to survive, even if he felt like he was dying without it.

He should've known better than to think he could hide anything from a master spy, though.

They were working a covert op in Kazakhstan. They couldn't risk bringing in the entire S.T.R.I.K.E. team due to the sensitivity of the mission. Steve was the only backup Natasha had in case the mission went south. He hadn't seen a mission go south like this before.

Their mole inside the mob they were infiltrating was already dead when Natasha in – the whole mission had been a trap set out for her. By the time Steve could get in to rescue her, she was bleeding from a knife wound in her shoulder.

Captain America could take out a dozen men singlehandedly without breaking a sweat. And he did that. Easily. But then the last of the men fell to the floor as he banged the criminals head with his shield, and he was assaulted with the smell of blood. Natasha's blood.

The heavenly scent permeated his senses, and he gasped, squeezing his eyes shut as if that would stop the onslaught on his senses. She smelt of cinnamon – a scent he associated with adrenaline – and strawberries and something citrus... It shouldn't be so tempting, but she smelt absolutely divine. She smelt – God, he couldn't believe he was thinking this – fucking delicious.

"Rogers?" Natasha sounded worried, and maybe a bit scared?

He opened his eyes and stared at her. He realised that he was panting hard, and felt a slight nick on the corners of his mouth, just slightly below his lower lip. One hand reached up to tough his canines that had elongated into fangs. "Oh, God."

"Rogers, what's going on?" She was trying to sound calm, but Steve could detect something akin to panic in her voice. She was fighting against her binds, but they were done too well.

Steve tried to focus on the mission. Natasha would bleed to death at the rate her wounds were bleeding. He took a deep breath and then held it as he clenched his jaws together and hurried behind her to tear the copper wires binding her wrists together in one strong tug. Gritting his teeth together, he swept her up in his arms and ran to the truck he had parked nearby. Some of the mobsters shouted as he ran past them, and then there were people shooting at them, but most of the bullets glanced off his shield slung over his back. One bullet grazed his bicep, but he hardly felt it. Placing her in the passenger seat of the truck, he took another gulp of air as he hurried over to the other side and drove. After ditching the chasing mobsters and the bloodied truck, he drove a S.H.I.E.L.D. issue SUV to a safe house.

Once he got her inside and safely placed on what he assumed was the first aid room, he ran and locked himself inside the bathroom. He splashed water on his face; it was ice cold and shocked some sense back into him. Grabbing the white utilitarian hand towel from the small rod next to the sink, he pressed it to his face, breathing into it as he willed his body to slowly calm down. He counted his breaths, going backwards from 10 and then repeating it. There was a banging on the bathroom door, and he tensed.

"Steve! Open up!" He didn't move a muscle, standing there, body rigid. Natasha banged on the door again, but he didn't respond.

"You realise that I'm bleeding out here?" She said calmly through the door, as if she was doing anything but bleeding to death. "As much as I like to think of myself as self-sufficient, I will need help in treating a stab wound in my shoulder."

Steve dropped the towel and turned towards the door, but he remembered his earlier reaction to the sight and smell of her blood. In all his previous 'experiments', he had never encountered anything like this and he didn't want to risk Natasha's safety. So he leaned slightly against the door, hands clenched into fists at his side to keep himself from opening the door, or breaking it.

"You need to get away from me, Natasha." He whispered, just loud enough that he knew she would hear.

It was silent on the other side of the door, but he knew better than to believe that she had left. A few moments later, as if she hadn't even heard him speak, she said, her voice now betraying all her pain and exhaustion, "Don't leave a girl hanging, Rogers."

Something inside him broke at her tone. His hand moved without any conscious thought to do so, and then he was opening the door. Natasha was on the floor beside the door, leaning against the wall, eyes drooping with fatigue and blood loss. She was holding a sterile white cloth to her bleeding left shoulder, but the top of her black dress was soaked with blood. Yet she smiled when Steve knelt next to her and carefully picked her up, carrying her to the single bed in the middle of the room. She settled against him, leaning her head in the crook of his neck even as he placed her on the twin bed.

He tore apart the top of her dress and removed the cloth from her wound to inspect it. "It's not very deep," he commented. His voice was strained as he held his breath.

"Amateurs," Natasha mumbled against the material of his uniform. "Don't even know how to hurt a person properly. I was very disappointed."

"You should be glad." He cleaned it with antiseptic and saline, making sure to wipe all the dried blood on her shoulder. With quick steady movements he sealed the wound and covered it with bandages. Once it was done, he grabbed a large clean shirt from a drawer and helped her get into it. Then he gently nudged her to roll onto her stomach and lie down. "Do not move your arm."

He got up to dispose of the bloody materials, taking off the top of his uniform on the way. Confident there was no more lingering smell of her blood in the room, he finally took a deep breath. Natasha turned her head to face him, moving her right arm under it to cushion it. "You wanna tell me what happened to make you go all Twilight on me?"

He got the confused crinkle between his eyebrows every time she made a pop culture reference that he hadn't managed to catch up on. "What on you?"

She considered explaining it to him, but then shook her head ever so slightly, careful not to jostle her shoulder. "You're better off not knowing." She studied him for a moment, standing awkwardly with his arms crossed across his chest, wearing only his undershirt and the tight pants of his stealth suit. He looked ridiculously good, even with that frown in his forehead that meant he was beating himself up over something that was probably not his fault again.

It was surprising how well they got along since Fury paired them up eight months back. He was the American symbol of purity; she was the Russian embodiment of a temptress – the very idea of them together was catastrophic. There were, like, a hundred and one Cold War jokes in S.H.I.E.L.D. She thought their very first mission – a stealth op – would end in disaster.

But they had somehow...clicked. Fury had given her a side mission of her own – because of course he had – and Rogers had been pissed, sure, but he looked so disappointed that even Black Widow felt guilty. They had been driving back to DC, and he had been chastising her.

"When I'm out in the field, I need to know that my partner will have my back. I can't do that when you have little side missions of your own that I don't even know about."

"Well, it's called compartmentalisation. Welcome to the 21st century, Captain."

"If we're going to be partners, we need to trust each other. Not compartmentalise. Back during the war, the Commandos and I trusted each other with our lives. That's how almost all of them ended up surviving it."

"This isn't World War II," she retorted. "The circumstances have changed."

"A war is a war. It doesn't matter if it's fought using nuclear weapons or a computer chip. You don't win a war by keeping secrets from a fellow soldier. You trust them."

"Is that what you need me to be? A soldier?"

"I don't need you to be a soldier. I need you to be a friend."

That day, she might have had a sassy remark waiting to be said, but whatever it was, it died on her lips. Steve Rogers had managed to ignite emotions in her that she had never felt before. She realised that the only person she did trust was Steve.

"Steve?" she drawled out, catching his attention once again.

"Yeah, Nat?" he imitated her cheekily, even though his heart was obviously not in it.

"We're partners, right?"

"Gee, really? What gives?"

She rolled her eyes, but a smile turned up on her lips. She loved that she got to see this sassy, sarcastic side of him. Captain America was every bit as good and moralistically virtuous as the history books said, but Natasha had soon found out he was also an adorable little piece of shit. Even though if she said that to him, he would probably – most definitely - reprimand her for her use of foul language. "What happened to the guy who lectured me on the importance of trusting your partner back on our very first mission?"

To his credit, Steve did look sheepish. She smiled gently at him and pulled her arm out from under her head and held it out to him, curling her fingers in a 'come here' motion. He sighed and walked over to her, grabbing her hand when he reached the bed and sitting down on the floor with his back leaning against the side of the bed. He let his head fall back against the mattress just next to her fingers – fingers that wasted not a moment in entangling themselves in his hair. His mother used to do that to him when he was sick, and Natasha had discovered the gesture calmed him after he had woken up from a horrible nightmare during a mission.

"Steve, tell me what's up with you before I beat it out of you."

He scoffed. She smacked him on his head.

"Ow," he said playfully. She knotted her fingers in his hair and jerked his head back. "Ow!"

And then she was right there bending over him, her face right above his, upside down, and she had one red eyebrow arched perfectly up and he almost groaned as all the hunger he felt for her when he saw her earlier slammed back into him. Natasha's eyes widened at his reaction, but she didn't let him go, didn't back down.

"Steve, talk to me," she whispered.

"It's the serum," he said, his voice husky, pupils dilated.

"Oh?" she raised an eyebrow sceptically.

"A side-effect."

"It's a pretty major side-effect," she said evenly.

"It doesn't happen all the time." He didn't know why he was defending it, but he felt the need to clarify.

She didn't budge, though. "So the super soldier serum turns you into a part-time vampire? I don't think undeath works that way, Steve."

There was a small hint of humour in her voice. He gulped, his face flushing. He was pretty sure his embarrassment was written all over his face. Natasha tilted her ever so slightly, her eyes narrowing, as she studied him. "Oh, this is going to be so good."

"I don't...need to drink...blood to survive," he managed.

"Mm-hm," she prompted.

"I just need it to...come."

She froze. Her face still above his, eyes level with his, with her fingers still tangled in his hair, she froze. The silence between them stretched for a few moments, almost tense, and then... she giggled. Black Widow, assassin extraordinaire, honest to God giggled.

Steve groaned, burying his face in his hands, and Natasha fell back against the bed, wincing only slightly from her injury as she laughed. "Nat, please, stop," He said miserably.

She pressed a fist to her mouth to hold in her giggles. She calmed down enough after a few moments. "Tell me everything." He hesitated, and she gave him a stern look. "Rogers, what happened to partners needing to trust each other?"

He sighed. She leaned back into the bed, getting comfortable for the story. He did not face her as he spoke, but she could see the red creeping up his neck and the side of his cheeks.

"It happened with a showgirl the first time. We were...in the middle of things, and before I knew it, I had my fangs in her neck, drinking her blood. I panicked, obviously, but I didn't feel the... bloodlust again. A few weeks later I was with another showgirl-"

"Whoa, Steve! You're telling me you were sleeping around?" she teased him.

He gave her a wry look, and continued. "This time, when I felt it, I controlled myself. I didn't bite her, but I also didn't...finish. So I took advice from Howard-"

"You took advice from Stark's father?!"

"-and he suggested I should conduct an... experiment."

"An experiment," she said incredulously.

"Yeah. Turns out, I can't have sex without wanting blood, and not satisfying one means not satisfying the other too."

Natasha let that sink in. "Huh." She was silent, contemplating, and then she chuckled. "So does that make you a vampire or a succubus?"

The noise he emitted was somewhere between a groan and a growl. "Neither, Nat! It makes me horny!"

"Oh my God!" she laughed. "The press would – no, Tony Stark would have a field day if he found out about this."

When he saw she was enjoying this a bit too much, he groaned and got up to leave. "You're horrible," he said grudgingly.

"No wait, Steve!" he was at the door when she stopped him.

He sighed and turned around. "Now what? Haven't you made fun of me enough?"

"I'm sorry," she pouted playfully, but he could see she meant it. She patted the spot on the bed next to her. "Stay?"

He made a show of reluctantly walking back, drawing out a smile from her, which quickly turned serious. "It doesn't explain what happened earlier, though."

"I don't know," he admitted, pressing the palms of his hands against his eyes for a moment before looking at her. "I got nothing. It's not happened with anyone else before. With you, it's way beyond physical gratification. I've felt this...lust for you since the moment we met. I can't explain it – it's almost like a craving for you."

She was quiet, her gaze downwards on where his thigh toughed hers. His hands lay on his lap, and she grasped his left one in her right. He looked at their entwined fingers first, then at her. She tugged at his hand, pulling him towards her, catching him off balance in his surprise, and he had to press his other arm into the edge of the mattress to steady himself.

She let go of his hand and cupped his cheek delicately. "Do you trust me?" she whispered.

"Nat, what-"

"Do you trust me, Steve?"

He studied her, searching her face. She had a determined set to the eyebrows, and her lips were drawn into a thin line. But her eyes were kind, and compassionate. His voice hoarse, he nodded, "Yes."

Her gaze drifted to his lips, and she leaned forward slowly, giving him enough time to back out. Just before her lips touched his, she hesitated, her gaze meeting his. He was frozen rigid, and she took it as a sign to move forward.

Their lips touched softly at first. They lingered there with the gentlest of pressure. And then Steve growled, his hands grabbing her face as he tilted it to deepen the kiss. His tongue darted forward to part her lips, his mouth capturing the lower one and sucking on it. She whimpered, her good hand sliding to the back of his neck and curling into the tiny hair over there tightly to keep him in place. When his tongue entered her mouth, she didn't fight him, but let him explore.

He shifted over her, moving one leg over to her other side to straddle her, and pushed her back onto the bed. The movement jostled her injured shoulder, and she let out a gasp of pain. He pulled back, his hand moving under her to lightly cradle her shoulder.

"We shouldn't do this," he gasped, breathing hard.

She pulled him back down on her. "No, this is what you need." She pressed her lips to his, and he kissed her back, before pulling away again.

"Your shoulder-"

"I've had worse," she cut him off. "I've had sex with worse."

"I won't be able to stop myself from taking your blood –"

"That was the plan..."

"But you've already lost blood –"

She cut him off with a firm kiss. "I can handle it, Steve." She patted his back, running her hands over it, feeling the muscles flex under her touch. "Besides, it's the Black Widow who kills her mate, not the other way round."

He chuckled, not completely satisfied with her answer but ready – and too goddamn desperate – to go on. He dipped his head and once again captured her lips in a searing kiss. Her arm wrapped round his back, she pressed his body down on hers, wanting to feel the contours of his chest against her supple curves. He groaned into her mouth, and she felt his very obvious erection press into her thigh. She lifted a leg from under him and curled it around his hip, the heel of her foot pressing into his ass, and pushed his pelvis to rub against her.

They both pulled away with gasps of pleasure and a desperate need for oxygen. Steve buried his face in the crook of her neck, running his nose along the line of her vein, inhaling. He placed a kiss just below her ear at her jugular, and she moaned. Glad to have found a sensitive spot, he wrapped his lips around it and sucked, leaving a very obvious love bite. Tilting her hips up, she rubbed her centre right against her clothed length, and he groaned, his teeth grazing her neck.

It was a flurry of movement after that as they hurried to get their clothes off. Steve helped Natasha take her shirt off carefully, and ripped off the remains of her dress from the night. She managed to pull his undershirt up halfway one-handed, and he tore it off. One arm still curled protectively around her shoulder, he pressed a kiss to her lips before trailing down. When his mouth reached her breasts, he was quick to latch on to a nipple, rolling it in his mouth with his tongue.

"Steve," she whimpered, her hand finding his head, fingers tangling in his hair – she was really fond of doing that – pressing him further into her chest. His unoccupied hand ran down the length of her, tracing up her arm, curving over her breast, down her toned stomach till it reached her black underwear. With his middle finger, he lightly traced over her covered slit, teasing. Pushing aside the lace, he teased her entrance before easily slipping one finger inside, causing her to moan.

He switched over to the other nipple as his finger started moving in and out of her in a steady rhythm. She was gasping loudly now, moaning with pleasure. When he slipped another finger in, her walls clenched tightly around him, and then she was pulling him up as her legs tried to push his skin-tight stealth suit off his hips.

"No more foreplay," she groaned against his lips. He agreed with her as he quickly had his legs free of the material. Grabbing his hard length, he pumped it a few times before lining it up with her entrance.

He filled her completely, the sensation leaving both of them breathless. He let her adjust to his girth, while he himself got accustomed to the heat gripping him. Then he pulled out slowly, and thrust back in hard. She gasped, her entire body shifting upwards with the thrust. Despite all the earlier urgency and desperation, they settled into a slow and gentle rhythm. His moved with long, hard thrusts and she met every single one of them. They took their time, tracing each other's bodies with their hands and lips. When her soft moans started turning into quiet whimpers, he knew she was close. He changed pace, moving faster now, and she clung to him, an unintelligible stream of his name mixed with praises and curses in Russian escaping her lips.

Her orgasm hit her suddenly and hard, and her walls clenched and squeezed his length. His hips kept thrusting, and he placed a kiss on her pulse before sinking his fangs in. Blood pooled in the two punctures in her neck, and he sealed his mouth over them.

It was like an explosion take place in his mouth. Her blood flowed in, tasting just as heavenly as it smelt, and he felt her own pleasure through it, amplified by the bite-induced endorphins. It sent her spiralling into another orgasm, and waves of pleasure rolling over him sent him over the edge. After almost seventy years of withdrawal, his pleasure was hard enough to – as cliché as it was – make stars appear in front of his eyes. Steve was vaguely aware of Natasha howling unfamiliar curses in pleasure.

They continued moving through their mutual release, prolonging the pleasure. When they finally stilled, Steve collapsed on top of her. His lips had long since let go of her neck, and her puncture wounds were already sealing. Gasping and panting, they both slowly came back to reality.

"Holy shit," Steve muttered, pressing his forehead into her uninjured shoulder.

"That is some bad language, there, Rogers," she couldn't help but tease. Her voice was hoarse from all the screaming. "You kiss your mother with that mouth?"

"I'm not as innocent as I look, you know."

"You just gave me multiple earth-shattering orgasms while drinking my blood from my neck. Trust me, I know."

"Besides," he leaned up and grinned down at her below him, "I'd rather kiss you with this mouth."

"Smooth," she said approvingly, and then his lips captured hers in a slow kiss. She quickly pulled back, though, grimacing. "You taste of blood."

"Sorry," he flushed, looking sheepish. "You okay?"

She hummed. "More than okay," she said, her words slightly slurred as the blood loss caught up to her. "Way more than okay."

He pulled out of her slowly, both of them wincing at the over-stimulating movement. He grabbed a bottle of water from the cooler in the room and helped her drink it. Once done, she leaned against him, obviously drained. He lay back on the bed and she curled up against his chest, the tiny bed not leaving them with much more options. His fingers carded through her sweat-drenched curls soothingly, and they stayed in this position for a long time.

"Where do we go from here?" Steve wondered.

Natasha turned her face and pressed a kiss to his naked chest. "We could settle into a friends-with-benefits situation, even though some of the normal rules probably won't apply here. We can tackle any problems as they come."

He contemplated that for a few minutes. "Okay."

"Yeah?"

"Yeah," he grinned down at her on his chest. "We're partners. We can do this."

She smiled back at him. "Yes, we can."

She settled back against his chest, and they fell asleep like that.

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 **Well, looks like you survived it. Send me your Hogwarts house and I'll give you five points because you deserve it.**

 **Also, feel free to check out my tumblr**

 **multi-fandom-crazy-fangirl**

 **Love, Sakshi.**


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